Collapse in self-gravitating turbulent fluids

Motivated by the non-linear star formation efficiency found in recent numerical simulations by a number of workers, we perform high-resolution adaptive mesh refinement simulations of star formation in self-gravitating turbulently driven gas. As we follow the collapse of this gas, we find that the character of the flow changes at two radii, the disc radius r(d) and the radius r(*), where the enclosed gas mass exceeds the stellar mass. Accretion starts at large scales and works inwards. In line with recent analytical work, we find that the density evolves to a fixed attractor, rho(r, t) -> rho(r), for r(d) < r < r(*); mass flows through this structure on to a sporadically gravitationally unstable disc and from thence on to the star. In the bulk of the simulation box, we find that the random motions v(T) similar to r(p) with p similar to 0.5 are in agreement with Larson's size-linewidth relation. In the vicinity of massive star-forming regions, we find p similar to 0.2-0.3, as seen in observations. For r < r(*), v(T) increases inwards, with p = -1/2. Finally, we find that the total stellar mass M-*(t) similar to t(2) is in line with previous numerical and analytic work that suggests a non-linear rate of star formation.